Drafters prepare working plans and detail drawings of products or structures from the rough sketches, specifications, and calculations of engineers, architects, and designers. These drawings are used in engineering or manufacturing processes to reproduce exactly the product or structure desired, according to the specified dimensions. The drafter uses knowledge of various machines, engineering practices, mathematics, and building materials, along with other physical sciences and extensive computer skills, to complete the drawings. There are approximately 205,190 drafters working in the United States.